Pierre Bertrand, MVL
Characterization of Spacesuit Kinematics and Human-Suit Interactions
There are multiple challenges associated with extravehicular activity (EVA). The design of a spacesuit requires specific attention to the mobility of astronauts. All of the currently flown spacesuits are gas-pressurized and can perform a wide range of functions. However, the pressurization causes an inherent stiffness, leading to astronaut's fatigue, unnecessary energy expenditure and impeded mobility. The goal of this study was to characterize the kinematics of the person inside the suit and to compare it to the kinematics of the suit as a result of the person's motion inside. The study was performed in two different suits: the David Clark Mobility Mockup and the NASA Mark III. The current industry standard to measure spacesuit kinematics is video motion capture. Although this technology allows external motion of the suit to be reliably measured, it does not measure the person's motions inside the suit. This technology is also restricted to laboratory settings due to equipment constraints. Inertial measurement units (IMUs) use accelerometers and gyroscopes to estimate relative translation and rotation. IMU systems are mobile and low-powered, offering an economical and efficient kinematic tracking capability. In this study, we applied IMU sensors to study space-suited motions. We placed IMUs on the lower arm, upper arm and torso, both inside and outside the suit. This configuration permits evaluation of the elbow and the shoulder joint angles, both internal and external to the suit. Subjects performed three types of isolated motions: elbow flexion/extension, shoulder flexion/extension and shoulder abduction/adduction. For each task, a comparison of joint angles between the human arm and the suit arm has been realized. A comparison of the angle's amplitude between the suited pressurized condition and either the suited unpressurized or unsuited condition was performed. The results show the different kinematic strategies between the human inside the suit and the suit. A significant impairment of mobility between baseline and pressurized conditions has also been demonstrated.